The deaths occurred over six days, with Indian media reporting that 30 children died on Thursday and Friday because of a lack of oxygen on the children's wards.

Suppliers' bills had allegedly not been paid, leading to a shortage that saw panicked families using artificial manual breathing bags to help their loved ones.

Local officials have conceded there was a disruption to the oxygen supply at the hospital in Gorakhpur, but insist the deaths were caused by encephalitis and other illnesses, not a lack of available oxygen.

"We are confident that none of the lives were lost because of this episode," a senior government health official in Gorakhpur said on Sunday.

But victims' families have disputed this, describing the panic and chaos as patients began struggling from a sudden lack of oxygen.

"As soon as we reached the hospital, we were handed a small pump and told to keep pumping. I did so for over three-and-a-half hours," one victim's father, Shailendra Gupta, was quoted by Sunday's Indian Express as saying.

"The next day, we were informed that he was dead."

Gorakhpur's police commissioner, Anil Kumar, said on Sunday that 11 more children had died at the hospital the day before.

"But I reiterate, they were not due to lack of oxygen supply," he added.

Doctors admitted that the oxygen supply had been disrupted for a couple of hours late on Thursday, but said no deaths had occurred at that time.

The hospital's breakdown of the death toll showed a jump on Thursday when 23 infants died, including 14 babies at its neo-natal unit.

The head of the hospital was stood down pending an inquiry into the oxygen shortage, which allegedly stemmed from nearly US$100,000 (Dh367,469) in overdue bills, some dating back to November.

As anger grew over the deaths, opposition parties and government critics led the charge for Mr Adityanath's resignation.

The firebrand Hindu priest, who won India's largest state in a landslide in March, toured the hospital wards on Sunday in his signature saffron robes and a blue medical mask and cap.

"This incident took place due to the laxity on the part of state government. The state government is fully responsible for it," Ghulam Nabi Azad, a senior leader of India's main opposition Congress party, said late on Saturday.

"The chief minister, health minister and the health secretary must immediately resign and doctors should not be blamed for this."